1. Field of the Invention
The present invention relates to a spindle motor.
2. Description of the Related Art
A hard disk drive (HDD), an information storage device, reads data stored on a disk or writes data to a disk using a read/write head.
The hard disk drive requires a disk driving device capable of driving the disk. In the disk driving device, a small-sized spindle motor is used.
The small-sized spindle motor has included a fluid dynamic bearing assembly. A lubricating fluid is interposed between a rotating member and a fixed member of the fluid dynamic bearing assembly, such that a shaft is supported by fluid pressure generated in the lubricating fluid.
In addition, in the spindle motor adopting the fluid dynamic bearing assembly, the lubricating fluid (oil) forms an air/oil interface at a boundary with air due to surface tension and a capillary phenomenon. A sealing part of the fluid is formed by using the air/oil interface.
However, oil may be leaked to the outside due to other factors and oil may be scattered by being diffused according to a concentration gradient of oil generated by a mole fraction difference. Therefore, a need exists for a method for reducing an amount of oil leaked due to diffusion.